The present invention relates to a projecting system for forming an image on a screen, especially to a technique for use in a simulator, a game equipment, a virtual reality equipment and the like for providing an image with a high feeling of presence to a viewer.
Recently, in this type of device, there is a rapidly increasing tendency to a desire for what provides a high feeling of presence. For this, an image providing a feeling of absorption is demanded, while there is a desire for a seat or the like driven to operate in accordance with an image, or a motion of an image operated interactively by a viewer.
As a projecting system giving a feeling of absorption or presence available is a HMD (head mounting display) which is a projecting system for one person. In the HMD, a small display is positioned immediately in front of viewer's eyes. An image on the display is enlarged by an optical system, so that a large virtual image of a remote object is shown to a viewer. In the system, since viewer's eyes are covered, the viewer cannot see anything but the image, and can be given a feeling of absorption. In the HMD, when a direction of a sight line or viewing direction is changed by shaking a head, the image projected on the display also is changed in accordance with the movement of the head, thereby providing an image of 360 degrees. Further, the HMD is advantageously small-sized. Such a projecting device is disclosed in, for example, the Japanese Patent Unexamined Publication No. 04-168489.
In addition to the HMD, as another method of providing an image having a feeling of absorption, a method of covering a visually recognized range of a viewer with a screen is available. To realize this method, a method of installing a projector for enlarging and projecting an image on a screen opposite to a viewer with respect to the screen or a method of installing the projector at the same side as the viewer with respect to the screen is available.
As a conventional method of installing the projector at the side opposite to the viewer with respect to the screen, for example, a projecting system with a cubic screen called CAVE is heretofore available (Virtual Reality, authored by Michitaka Hirose, Sangyo Tosho, p101). In this CAVE, four rear projection screens with about 3 m sides are disposed for use in such a manner that the respective screens have an almost right angle relative to one another and are positioned in front, left, right and lower directions, respectively, and each screen is provided with a projector. Additionally, other methods are described in the Japanese Patent Unexamined Publications No. 5-197329 and No. 6-503906. In either of these, several flat rear projection screens are used, and each face is provided with a projector.
Also, in a conventional method of installing the projector at the same side as the viewer with respect to the screen, a reflective screen having a spherical configuration and a projector using a fisheye lens are used. The spherical reflective screen is usually constituted by using small spherical screen parts and assembling them up into a spherical screen.
Generally, a range of sight which can be recognized without moving a head and by hardly moving eye balls (hereinafter, referred to as the visually recognized range) is said to be about 120.degree. both in horizontal and vertical directions when left and right eyes are used. A range of sight which can be recognized without moving the head and by moving the eye balls (hereinafter, referred to as the sight range) is said to be about 240.degree. in the horizontal direction and about 180.degree. in the vertical direction when either one of the eyes is used. An image which can cover the visually recognized range of both eyes can remarkably provide a feeling of presence. In either of the aforementioned conventional methods of covering the sight range of a viewer with the screen, a screen with a size of 120.degree. or more centering on the viewer is used, which can sufficiently cover the visually recognized range of the viewer. Further, in the HMD, since an image range is about from 60.degree. to 80.degree., there easily arises a puppet theater effect in which an image is felt small. However, since the sight range is completely covered, a feeling of absorption is remarkably provided.
However, in the HMD, when a viewer changes a direction of a sight line by moving his head, a change in an image on a display causes a time lag relative to movement of the head. There is a problem that the viewer has a strange feeling in the image so as to spoil the feeling of presence. Further, since the HMD is mounted on the viewer's head, the oppression on the head causes a strange feeling. Additionally, there is a problem that cleanliness can hardly be kept for use by another viewer.
On the contrary, in the method of covering the visually recognized range of a viewer with the screen, even when the viewer changes a direction of a sight line, an image always exists also in the changed direction of a sight line, thereby causing no time lag in the image. Further, since no device is mounted on the viewer's head, the oppression on the head is not produced. This is furthermore preferable in respect of hygiene. Specifically, the method of covering the visually recognized range of the viewer with the screen causes no problem the HMD has. However, even this method has the following problems.
In the method of covering the visually recognized range of the viewer, when the projector is installed at the same side as the viewer with respect to the screen, the projector, in addition to the viewer, is disposed inside the screen. Therefore, if the projector is not disposed at a position which does not obstruct the screen from the viewer, a feeling of presence will be spoiled. Especially, if the viewer and the projector are disposed in a small-sized screen with a diameter of about 5 m which is supposedly a limitation in size able to be housed inside a generally commercial building, then the projector itself obstructs the range of a sight line of the viewer. Additionally, there is a case that the image to be projected on the screen from the projector is obstructed by the viewer himself. In this case, a feeling of presence is spoiled. Further, a spherical screen is usually formed by assembling divided parts. A problem is that the joint portion of the screen can be seen by the viewer, thereby spoiling a feeling of presence.
Further, when the projector is installed opposite to the viewer with respect to the screen, in either of the aforementioned prior arts, nothing obstructs a sight line of the viewer inside the cubic screen. However, since a large number of flat screens are assembled, each boundary line between the screens forms a mathematically discontinuous portion (bent portion). A problem is that the viewer recognizes discontinuity in an image with the discontinuous portions of the screen, and a feeling of presence is spoiled.